Hexadecyl 2-ethylhexanoate

Toxicity to soil macroorganisms except arthropods

Description of key information

LC50 (14d) > 1000 mg/kg soil dw (read across)

Additional information

There are no data available for the acute toxicity to terrestrial macroorganisms of Hexadecyl 2-ethylhexanoate (CAS No. 59130-69-7). In order to fulfil the standard information requirements set out in Annex VII - IX, 9.1, in accordance with Annex XI, 1.5, of Regulation (EC) No 1907/2006, read-across from structurally related substances was conducted.

In accordance with Article 13 (1) of Regulation (EC) No 1907/2006, "information on intrinsic properties of substances may be generated by means other than tests, provided that the conditions set out in Annex XI are met.” In particular, information shall be generated whenever possible by means other than vertebrate animal tests, which includes the use of information from structurally related substances (grouping or read-across).

Having regard to the general rules for grouping of substances and read-across approach laid down in Annex XI, 1.5, of Regulation (EC) No 1907/2006, whereby substances may be predicted as similar provided that their physicochemical, toxicological and ecotoxicological properties are likely to be similar or follow a regular pattern as a result of structural similarity.

Terrestrial Toxicity of the target substance Hexadecyl 2-ethylhexanoate (CAS No. 59130-69-7) and the source substance Hexanoic acid, 2-ethyl-, C16-18 alkyl esters (CAS No. 90411-68-0) are presented in the following table.

CAS	59130-69-7	90411-68-0
Chemical name	Hexadecyl 2-ethylhexanoate	Hexanoic acid, 2-ethyl, C16-18 alkyl esters
MW	368.6 g/mol	368.6-396.7 g/mol
Toxicity to soil macroorganisms except arthropods	RA: CAS 90411-68-0	LC50 > 1000 mg/kg soil dw
Toxicity to terrestrial arthropods	Waiving	--
Toxicity to terrestrial plants	Waiving	--
Toxicity to soil microorganisms	Waiving	--

The above mentioned substances are considered to be similar on the basis of the structural similar properties and/or activities. The available endpoint information of Hexanoic acid, 2-ethyl-, C16-18 alkyl esters (CAS No. 90411-68-0) for acute terrestrial ecotoxicity is used to predict the same endpoint for Hexadecyl 2-ethylhexanoate (CAS No. 59130-69-7).

A detailed analogue approach justification is provided in the technical dossier (see IUCLID Section 13).

Discussion

Read across acute terrestrial ecotoxicity

No studies investigating the acute toxicity of Hexadecyl 2-ethylhexanoate (CAS No. 59130-69-7) to terrestrial microorganisms are available. Therefore in accordance with Article 13 (1) of Regulation (EC) No 1907/2006, a read across to Hexanoic acid, 2-ethyl-, C16-18 alkyl esters (CAS No. 90411-68-0) was applied for the acute test to earthworm (OECD 207). A read across from Hexanoic acid, 2-ethyl-, C16-18 alkyl esters to Hexadecyl 2-ethylhexanoate to cover the short-term toxicity to earthworm is acceptable as first, both substances have common functional groups being esters of 2-ethylhexanoic acid and fatty alcohols with carbon chain lengths of C16 - C18 and C14 - C18, respectively. Second, both substances have the common precursor 2-ethylhexanoic acid and fatty alcohol and common breakdown products as both are expected to be rapidly metabolised in the body via enzymatic hydrolysis to the starting materials (e.g., see Barron et al. 1999 for metabolism of esters in fish), which then fed into body’s natural catabolic processes, such as ß-oxidation and citric acid cycle (e.g., Rahn et al., 1973; Henderson, 1996).  Based on their structural similarity the physico-chemical properties are also similar. Both substances are insoluble in water (< detection limit of used method), feature similar partition coefficients of 5.82 (CAS No. 90411-68-0) and 6.15 (CAS No. 59130-69-7) and the main components of the UVCB substances have similar molecular weights of 368.6 - 396.7 (CAS No. 90411-68-0) and 368.6 (CAS No. 59130-69-7). The volatility of both substances is low (< 0.01 Pa at 20 °C). Hence, the behaviour, the fate, the bioaccumulation and thus the toxicity of the substances in the terrestrial environment are considered to be identical.

Results terrestrial ecotoxicity

One study investigating the short-term toxicity to earthworm of the read across substance Hexanoic acid, 2 -ethyl, C16 -C18 alkyl ester (CAS 90411 -68 -0) is available. The study was performed as a limit test according to OECD guideline 207 and GLP (Harris, 2013). The test organism Eisenia fetida was exposed to the test substance in artificial soil for 14 days, at the nominal test concentration 1000 mg/kg. No mortality occurred during the test period. Hence, the test substance is not expected to have effects on soil macroorganisms. No further studies on terrestrial organisms are available for this substance.

Due to structural and property similarities to the read-across substance Hexanoic acid, 2-ethyl-, C16-18 alkyl esters (CAS No. 90411-68-0) this result is also applicable to read across to to Hexadecyl 2-ethylhexanoate (CAS No. 59130-69-7).

No further experimental data evaluating the toxicity to soil organisms is available for Hexadecyl 2-ethylhexanoate (CAS No. 59130-69-7). Due to the ready biodegradability of the substance only negligible amounts, if at all, are expected to be present in the terrestrial compartment. Therefore chronic exposure of terrestrial organisms is unlikely. Furthermore, the substance is not toxic to aquatic organisms up to the limit of water solubility. In addition, available data indicate, that Hexadecyl 2-ethylhexanoate (CAS No. 59130-69-7) is not bioaccumulative. Based on the available information, toxicity to terrestrial macroorganisms is not expected to be of concern.

A detailed reference list is provided in the technical dossier (see IUCLID, section 13) and within the CSR.